Introducers for implantable leads and catheters typically include a dilator and an associated introducer sleeve, through which the lead or catheter is to be inserted. Conventional designs of lead and catheter introducers are disclosed in U.S. Pat. No. 4,306,562 issued to Osborne, U.S. Pat. No. 4,596,559 issued to Fleischhacker and U.S. Pat. No. 4,166,469 issued to Littleford. In conjunction with such introducers, it has become common to include a hemostasis valve. Introducers including hemostasis valves are illustrated in U.S. Pat. No. 5,672,158 issued to Okada et al., U.S. Pat. No. 5,098,393 issued to Amplatz et al. and U.S. Pat. No. 5,312,355 issued to Lee. In all such cases, the hemostasis valve engages the circumference of the lead or catheter to be introduced.